The subscapularis is the largest and strongest of the rotator cuff muscles and is located in front of the scapula in a triangular shape. Starting from the subscapularis fossa, the muscle bundle goes up through the front of the scapular joint and ends at the humeral tuberosity. The function is to internally rotate the scapular joint, while providing anterior stabilization of the scapular joint and force couple around. Subscapularis tendon injuries are common in clinical practice, but because of the deep location of this muscle, patients have symptoms and cannot accurately point out the lesion site, and physicians often do not pay attention to it, which often leads to missed diagnosis. Injuries to the subscapularis tendon are most often caused by trauma from external rotation or repeated impingement under the rostral process when the shoulder joint is outstretched. Long-term continuous internal retraction and internal rotation of the upper limb can lead to repeated contraction of the subscapularis muscle, resulting in slight tearing of the tendon fibers at the humeral tuberosity stop and destruction of small blood vessels, leading to tendon tears in the long term. Clinical manifestations: pain in the front of the shoulder joint, soreness and discomfort in the scapula. The pain increases with external rotation of the shoulder joint and decreases in internal rotation position. Unlike the clinical manifestations of supraspinatus and infraspinatus injuries, pain from a subscapularis tear is usually associated with reduced range of motion of the affected shoulder below the shoulder level, and patients often resort to scapular motion as a substitute for some of the shoulder motion. Physical examination: Lift – off test (Figure 1): The dorsum of the affected upper extremity is placed against the lower lumbar back. The patient is asked to internally rotate the forearm so that the dorsum of the hand leaves the lower lumbar back posteriorly; if the patient cannot leave the lower lumbar back posteriorly, the test is considered positive. It is more sensitive in the diagnosis of total laceration. Compression test (Figure 2): the patient places the palm of the affected upper limb against the upper abdomen. If the patient can straighten the wrist joint and apply pressure to the abdomen, the test is negative; if the patient flexes the wrist joint at 90° before applying pressure to the abdomen, the test is positive and a complete tear of the subscapularis tendon is considered. If the patient is able to apply pressure to the abdomen only after 30-60° of wrist flexion, a partial tear of the subscapularis tendon is considered. Diagnosis: 1. History of trauma or strain; 2. Pain and pressure at the humeral tuberosity at the subscapularis stop. 3, positive Lift – off test or compression test 4, MRI (Figure 3) or ultrasound showing subscapularis tendon injury Treatment: rest, braking Physical therapy Oral NSAID medication Conservative treatment is not effective Consider arthroscopic repair Figure 1 Figure 2 Figure 3